1. Field of the Invention
The invention relates to the field of variable moment of inertia flywheels and most particularly to that field in which the moment of inertia is varied by hydraulic means.
2. Prior Art
A flywheel is a wheel designed to preserve or store momentum. It is most frequently used with a machine which is called upon to do considerable work but in which the work demand is not constant. Typically the flywheel is made with a heavy rim. As it acquires speed, its inertia assists in maintaining that speed, so that any sudden call for extra power is available immediately, and any tendency of the machine to run away or race, because of a sudden easing of the load, is avoided. In addition to its role of balancing a machine subject to a regular demand, the flywheel overcomes the problem of a dead center usually associated with devices for converting linear to reciprocating motion. At dead center all of the forces act along a radial line through the center of rotation. There is no moment created about the center at that point. The flywheel, with its inertia, carries the linkages through dead center to the point where the external driving force no longer acts through the axis of rotation and provides a moment of inertia about that axis.
The principles of the flywheel comprise inertia and centrifugal force. A rotating body tends to continue its motion and resist any change either of acceleration or retardation. The heavier the body is, and the larger its diameter, and the faster its speed, the more it resists change, because of its inertia. A heavy flywheel when speeded gradually becomes a store of energy. Thus, if there should be a sudden demand for an excess of power, with no apparent change in speed, as when a heavy metal press is placed into operation, the mechanism, with the aid of the flywheel, moves continuously without stopping or jerking. Thus the flywheel tends to equalize the load on the drive mechanism. The four-cycle combustion engine could not be operated at all without a flywheel, as the combustion cycle provides for an explosion only once in every four revolutions of the engine crankshaft.
In an internal combustion engine, a flywheel is located at one end of the crankshaft and serves to store up energy from the power stroke and supply it during the other three strokes. Since there is an overlapping of power strokes in a multicylinder engine, the size or the weight of the flywheel is reduced as the number of cylinders increases. The effect of a very heavy fly-wheel is to decrease the acceleration of the automobile because of the power that is required to increase the speed of the heavy flywheel. However, if the flywheel is made too light, surges of engine speed may be communicated to the transmission, which would be undesireable. Thus, in automotive design practice, a compromise is made in the determination of the size of the fly-wheel.
The problem of getting a machine up to speed when it is coupled to a heavy flywheel is not peculiar to automotive design. As early as Jan. 29, 1918, a U.S. Pat. No. 1,254,694, was issued to Humphries for a flywheel which, "will offer but slight resistence to rotation of the wheel when starting, but when the engine or mechanism begins to make up its speed . . . weight will move . . . to the rim where (the wheel) . . . will exercise its inertia in maintaining a substantially uniform speed of rotation." Humphries wheel was limited in that it had to be operated in a horizontal plane. He taught the use of a fluid or a pseudofluid (balls) which would move from the hub of the flywheel to its rim as the wheel was brought up to speed. Once the wheel had achieved speed its moment of inertia remained constant, Humphries having provided no means for varying the moment of inertia.
On Dec. 5, 1929, British Pat. No. 322,306 was issued to Thomas, a citizen of France. His flywheel is somewhat reminiscent of that of Humphries in that it was a dish-shaped flywheel which was limited in its operation to a horizontal plane. The dish was empty when its rotation was first started and therefore its moment of inertia was low and the starting couple was strong. As the wheel was brought up to speed, liquid was introduced into the dish-shaped chamber of the wheel and was acted upon by centrifugal force so as to move towards the rim of the dish and yield the rotating device a large moment of inertia. Unlike Humphries, Thomas provided his fluid from an external source and therefore could control the amount of fluid injected into the wheel and thus establish some control over the resultant moment of inertia.
In U.S. Pat. No. 2,404,515 issued to Meyer on July 23, 1946, and in U.S. Pat. No. 3,360,924 issued to Davis on Jan. 2, 1968, flywheels are disclosed which use fluid to obtain their mass. Neither one of them teaches the use of the fluid to provide an easily started, low moment of inertia flywheel. Meyer proposes the use of the hydraulic flywheel to conserve metal that would otherwise be required to achieve the necessary mass and to provide a wheel that could be easily dismantled or separated for purposes of repair or replacement of parts. Davis used fluid in his flywheel device in the hopes that liquid exhaust jets at the periphery of the wheel, which were operative to exhaust the liquid from the wheel when the wheel lost its drive power, would provide necessary reaction force at the exhaust jets to maintain the wheel at a reasonably constant speed of revolution until drive power could be re-initiated.
It is an object of the present invention to provide a flywheel which may be started rapidly because of its initial low moment of inertia and which, having achieved speed, may have its moment of inertia increased to an optimum level as determined by the machinery with which it is used and the nature of the load demand placed upon it.
It is a further object of the invention to provide a flywheel whose moment of inertia may be infinitely, and controllably variable during the course of operation of said flywheel.
It is another objective of the invention to provide a flywheel which may be rotated in any plane while still providing an infinite variability in the moment of inertia of the wheel.